The goal of this observational study is to learn about the ability of Phenotypic Age Acceleration (PhenoAgeAccel) to predict four key health outcomes in Chinese people with or at risk of major chronic diseases: the risk of developing new chronic diseases, the risk of dying, life expectancy, and disease-free healthspan.

The main questions this study aims to answer are:

• Does higher PhenoAgeAccel increase the risk of developing major chronic diseases (including diabetes, dementia, cancer, and chronic respiratory diseases) in Chinese adults?
• Does higher PhenoAgeAccel increase the risk of death from all causes in Chinese adults?
• How do life expectancy and disease-free healthspan differ between people with high versus low PhenoAgeAccel?

Who can take part in this study? Adults aged 35 or above years old who receive routine care at participating hospitals in China, have complete routine blood test data available, and have provided consent to use their health information for research purposes.

What will participants go through? Participants will receive their usual medical care as they normally would. No new treatments, tests, or procedures will be performed specifically for this study. We will collect data from their medical records, including blood test results used to calculate PhenoAgeAccel, diagnoses of new diseases, and dates of death.

What are the potential benefits? Participants will not receive direct personal benefits from taking part in this study. However, the information learned may help us better understand biological aging and improve future risk assessment and health management for people with chronic diseases.

Is this study safe? Yes. This is an observational study that does not involve any new drugs, devices, or invasive procedures. All data used in the study will be de-identified and kept strictly confidential to protect participants' privacy.

Inclusion Criteria:

• Adults aged 35-73 years old. Complete routine blood test data available at baseline to calculate Phenotypic -Age (including albumin, alkaline phosphatase, creatinine, glucose, C-reactive protein, lymphocyte percentage, mean corpuscular volume, red cell distribution width, and white blood cell count).

Complete demographic and clinical data (e.g., sex, BMI, comorbidities) available at baseline.

• Consent to use routine medical data for research follow-up analysis.

Exclusion Criteria:

• Presence of end-stage diseases (e.g., end-stage liver/renal failure) other than the major chronic diseases of interest at baseline.
• Key baseline data missing, making Phenotypic Age calculation impossible. Incomplete follow-up information or inability to confirm outcomes (e.g., death, disease onset) via database linkage.
• Refusal to participate in the study or withdrawal of informed consent.

The study population consists of Chinese adults aged 35-73 years from multicenter clinical cohorts in northern and southern China, with complete routine blood test data available at baseline. All participants are patients receiving routine care at collaborating hospitals. Data are prospectively collected via electronic medical records to analyze the association between Phenotypic Age Acceleration and major chronic disease and mortality outcomes.